Haunter to Gengar
Oddish to Gloom
Dratini / Dragonair to Dragonite
Looking at the first two forms of this evolution, you’d be forgiven for thinking that you were going to end up with some kind of awesome Chinese-style dragon, flying around and eating the sun and whatnot. Instead you get Dragonite, the Pokemon universe’s version of Barney the Dinosaur. He looks like Charizard’s older brother, the one who was a promising high-school athlete and the coolest guy in town until he graduated, couldn’t get a decent job because he’d spent all his time having Pokemon battles with the prom queen instead of studying and ended up working at a used car showroom. You’re a disappointment to us all, Dragonite.
Two reasons: It loses its legs when it evolves, which seems a little harsh, and the name "Weepinbell" sounds like a truly revolting venereal disease.
Bellsprout to Weepinbell
Koffing to Weezing
And there you go. Do nature a favour: let these Pokemon be.